I loved this piece, not just because of the nostalgia regarding my CSCW days, but also because SubEthaEdit was a ground-breaking application that I used extensively. Coda uses its engine, but sadly there has been very little activity in the field (although I’m currently tracking not one, but two a nodejs-based Etherpad clones that are quite promising, albeit not as useful – by a long shot – as a native app).